A very soft, silvery white metal which tarnishes quickly in moist air but which is stable if kept away from oxygen under water. Highly toxic.

Lump under water.
Thallium is one of the most toxic elements in the periodic table. It disrupts the normal metabolism of many cells by substituting for potassium. The result is fatigue, numbness, blackouts and hair loss. There are contradictory estimates of the lethal dose in the literature ranging from a gram down to just one twentieth of a gram. It was once an effective murder weapon before its effects became well understood and an antidote - prussian blue - discovered.Source: ChinaSize: 1.5"Purity: 99.9%